Dry eye symptoms are known to be caused by reduced rate of blinking due to overuse of eyes by “watching” television, computer screen, mobile computers, or the like, or by evaporation of lacrimal fluid due to dry air created by air conditioning. It has been reported that soft contact lens wearers, compared to non-soft contact lens wearers, tend to suffer from dry eye symptoms, due to increased evaporation of lacrimal fluid from the soft contact lens surface (Non-patent Publication 1). For relief or treatment of dry eye symptoms, supplementation of lacrimal fluid with an ophthalmic solution, i.e., artificial tear preparations, is commonly employed. Almost all such ophthalmic solutions contain preservatives for ensuring the product quality during a certain circulation period (Non-patent Publication 1).
Typical preservatives contained in ophthalmic solutions are benzalkonium chloride and hexamethylene biguanide hydrochloride. Even at a content of as low as not more than 0.01% w/v (weight/volume), benzalkonium chloride and hexamethylene biguanide hydrochloride are known to be adsorbed on soft contact lenses (Non-patent Publications 2 and 3). These compounds are also reported to have adverse effects on corneal cells, and may further cause eye damages (Non-patent Publication 4). In this regard, researches have been made to reduce the adverse effects of the compounds on corneal cells (Patent Publications 1, 2, and 3).
On the other hand, the trace preservatives are also known to be adsorbed on eye droppers or the like, as disclosed in Patent Publications 4 and 5, and this may cause gradual decrease of the active preservatives in the eye dropper, to result in weakened preservative effect.
In view of the above, for avoiding contamination of the eyes with microorganisms even when the preservative effect of ophthalmic solutions is weakened, package inserts of the ophthalmic solutions provide warnings for administration and expiration date. Irrespective of this, it is reported that some patients administer an ophthalmic solution with the tip of the eye dropper nozzle in contact with their ocular surface (Non-patent Publication 5). By contacting the tip of the eye dropper nozzle with the ocular surface, the interior of the eye dropper may be contaminated with microorganisms, which gives rise to not a little risk of developing infectious eye diseases.
Patent Publication 1: JP-2006-282586-A
Patent Publication 2: JP-H10-324634-A
Patent Publication 3: JP-H07-166154-A
Patent Publication 4: JP-2010-106015-A
Patent Publication 5: JP-2008-88174-A
Non-patent Publication 1: Supervised by Yoshihisa Oguchi, Edited by Kazuo Tsubota, Ocular Surface no Shindan to Chiryo (Diagnosis and Treatment of Ocular Surface), Medical-Aoi Publications, Inc., pp83-87, 1993
Non-patent Publication 2: Charles H. Powell et al., Lipophilic versus hydrodynamic modes of uptake and release by contact lenses of active entities used in multipurpose solutions, Contact Lens & Anterior Eye, 33, 9-18, 2010
Non-patent Publication 3: Takashi Sakimoto, Chiryo-you Kontakuto Renzu heno Boufuzai no Kyuchaku (Adsorption of Preservatives on Therapeutic Soft Contact Lenses), Journal of Japan Contact Lens Society, 35, pp177-182, 1993
Non-patent Publication 4: Edited by Yuichi Ohashi, Ganka (Ophthalmology) New Insight 2, Tengan-yaku-Joshiki to Hijoshiki (Ophthalmic Solution—Common Sense and Preposterousness), Medical View Co., Ltd., pp36-43, 1994
Non-patent Publication 5: Yuichi Ohashi, Ganka (Ophthalmology) New Insight 2, Tengan-yaku-Joshiki to Hijoshiki (Ophthalmic Solution—Common Sense and Preposterousness), Medical View Co., Ltd., pp56-65, 1994